Update babylon.animation.ts

Return the animatable for customization (onanimationEnd for example)

Babylon/Animations/babylon.animation.ts

@@ -41,7 +41,7 @@
 
             mesh.animations.push(animation);
 
-            mesh.getScene().beginAnimation(mesh, 0, totalFrame,(animation.loopMode === 1));
+            return mesh.getScene().beginAnimation(mesh, 0, totalFrame,(animation.loopMode === 1));
 
         }
 
@@ -395,4 +395,4 @@
             return Animation._ANIMATIONLOOPMODE_CONSTANT;
         }
     }
-} 
+}